The United States Department of Agriculture reported 1999 beef sales to be in excess of $50 billion dollars. Product loss caused by deaths in the herd during the same period were 1.4% of the herd total. 61.5% of these deaths were attributable to 10 Bovine Respiratory Disease (BRD). Losses from deaths caused by BRD were estimated to be $455 million dollars in beef cattle. In addition to mortality, BRD is the major cause of sickness in feed yard cattle, with morbidity rates of 50% not uncommon.
Even when successfully treated for BRD, morbid calves experience reduced overall weight and decreased feed efficiency during the feeding period and produce a carcass with decreased grade quality for the packer. In an industry with annual sales in excess of $50 billion dollars, overall BRD losses resulting from death, treatment costs, labor, and decreased feedlot and carcass performance amount to approximately one billion dollars annually. Early detection and prevention of BRD is a major challenge and a problem for the beef industry.
Furthermore, in many animal husbandry areas such as chicken, pig and sheep farming, herd health issues can cause tremendous financial loss to farmers, brokers, and packers. Often infectious diseases having an adverse impact on herd health remain undetected until a significant portion of a herd is affected, resulting in increased treatment costs and lower value herds.
Several herd management factors contribute to the high incidence of BRD in cattle. Many calves in the U.S. have a limited vaccination program, have no pre-weaning and are taken directly from the cow to sale at a local auction barn without benefit of any prior health management program. Buyers at auction often combine calves from multiple purchase sources for shipment to feed yards. During the marketing process, calves are subjected to a variety of health stressors and are exposed to both bacterial and viral pathogens. On arrival at the feed yard, calves are typically penned and exposed to feed and water sources generally unknown to them. Unweaned calves will have little feed intake for the first few days as they often spend their time walking the pen fence and bawling. This creates additional stress in the animal and opportunity for sickness in transition.
Early intervention or mass medication of animals upon arrival at a feed yard has been shown to reduce morbidity and mortality rates from BRD for high-risk calves. Although effective, this procedure is quite expensive and results in the administration of antibiotics to many calves that don't require them. When calves contract BRD, their body temperature begins to increase measurably often days before visual symptoms are present.